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exec.go
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exec.go
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//This package is copied from Go library text/template.
//The original private functions indirect and printableValue
//are exported as public functions.
package template
import (
"fmt"
"reflect"
)
var Indirect = indirect
var PrintableValue = printableValue
var (
errorType = reflect.TypeOf((*error)(nil)).Elem()
fmtStringerType = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
)
// indirect returns the item at the end of indirection, and a bool to indicate if it's nil.
// We indirect through pointers and empty interfaces (only) because
// non-empty interfaces have methods we might need.
func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
for ; v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface; v = v.Elem() {
if v.IsNil() {
return v, true
}
if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
break
}
}
return v, false
}
// printableValue returns the, possibly indirected, interface value inside v that
// is best for a call to formatted printer.
func printableValue(v reflect.Value) (interface{}, bool) {
if v.Kind() == reflect.Ptr {
v, _ = indirect(v) // fmt.Fprint handles nil.
}
if !v.IsValid() {
return "<no value>", true
}
if !v.Type().Implements(errorType) && !v.Type().Implements(fmtStringerType) {
if v.CanAddr() && (reflect.PtrTo(v.Type()).Implements(errorType) || reflect.PtrTo(v.Type()).Implements(fmtStringerType)) {
v = v.Addr()
} else {
switch v.Kind() {
case reflect.Chan, reflect.Func:
return nil, false
}
}
}
return v.Interface(), true
}
// canBeNil reports whether an untyped nil can be assigned to the type. See reflect.Zero.
func canBeNil(typ reflect.Type) bool {
switch typ.Kind() {
case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
return true
}
return false
}
// isTrue reports whether the value is 'true', in the sense of not the zero of its type,
// and whether the value has a meaningful truth value.
func isTrue(val reflect.Value) (truth, ok bool) {
if !val.IsValid() {
// Something like var x interface{}, never set. It's a form of nil.
return false, true
}
switch val.Kind() {
case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
truth = val.Len() > 0
case reflect.Bool:
truth = val.Bool()
case reflect.Complex64, reflect.Complex128:
truth = val.Complex() != 0
case reflect.Chan, reflect.Func, reflect.Ptr, reflect.Interface:
truth = !val.IsNil()
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
truth = val.Int() != 0
case reflect.Float32, reflect.Float64:
truth = val.Float() != 0
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
truth = val.Uint() != 0
case reflect.Struct:
truth = true // Struct values are always true.
default:
return
}
return truth, true
}